In the immune system, T-cells have at least two major functions; (i) they kill cells that appear foreign, e.g. cells that have been infected with viruses and carry viral antigens; and, (ii) they regulate other immune responses, including B cell antibody production. While the interleukins and a host of lymphokines have been described as effecting positive modulation of the immune response, it has become increasingly evident that the cells responsible for their production are also responsible for the production of other lymphokine-like proteins. Rather than effect positive immune response modulation, these proteins are involved in the "down"0 regulation of the immune system. As a result of their suppression regulating effect, these proteins have been collectively termed T-cell suppressor inducer factor, "TsFl".
Antigen-specific as well as antigen non-specific suppression of the immune response has been demonstrated in a variety of models including leprosy, pregnancy and tumors. However beyond the demonstration of the role and existence for TsFl, the biochemical and molecular genetic proof for the existence of TsFl has been lacking. No clear consensus has emerged as to the biochemical structure for TsFl. For example, the preliminary biochemistry for each TsFl varies depending on the reporting laboratory. Mr variances from 19,000 to 90,000 or even larger than 200,000 have been reported. While other T-cell related genes have been cloned and isolated, e.g. U.S. Pat. No. 4,713,332 disclosing a cDNA clone for T-cell antigen receptor, the isolation and cloning of the gene for a TsFl or any portion thereof has not been reported.
Hence, prior to isolating and cloning of the nucleic acid sequence of the present invention, a need existed for the isolation and molecular characterization for a TsFl and the gene which encodes for it. By so doing, antibody to TsFl may be prepared and used to identify cells which produce TsFl and to perhaps inhibit the down regulatory action of TsFl on the immune system. Further, such antibody could be used to measure and quantitate TsFl in vivo. Finally, the characterization of the amino acid sequence for a TsFl may also be used to produce antibodies which may be used for diagnosis and treatment of human diseases exhibiting a suppressed immune response.